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The spacecraft, Mars Reconnaissance Orbiter, will provide more science
data than all previous Mars missions combined.

Signals received from the spacecraft at 2:16 p.m. Pacific Time after
it emerged from its first pass behind Mars set off cheers and applause
in control rooms at NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
and at Lockheed Martin Space Systems, Denver.

"This is a great milestone to have accomplished, but it's just one of
many milestones before we can open the champagne," said Colleen Hartman,
deputy associate administrator for NASA's Science Mission Directorate.
"Once we are in the prime science orbit, the spacecraft will perform
observations of the atmosphere, surface, and subsurface of Mars in
unprecedented detail."

The spacecraft traveled about 500 million kilometers (310 million miles)
to reach Mars after its launch from Florida on Aug. 12, 2005. It needed
to use its main thrusters as it neared the planet in order to slow itself
enough for Mars' gravity to capture it. The thruster firing began while
the spacecraft was still in radio contact with Earth, but needed to end
during a tense half hour of radio silence while the spacecraft flew behind Mars.

"Our spacecraft has finally become an orbiter," said JPL's Jim Graf, project
manager for the mission. "The celebration feels great, but it will be very
brief because before we start our main science phase, we still have six
months of challenging work to adjust the orbit to the right size and shape."

For the next half-year, the mission will use hundreds of carefully calculated
dips into Mars' atmosphere in a process called "aerobraking." This will shrink
its orbit from the elongated ellipse it is now flying, to a nearly circular
two-hour orbit. For the mission's principal science phase, scheduled to begin
in November, the desired orbit is a nearly circular loop ranging from 320
kilometers (199 miles) to 255 kilometers (158 miles) in altitude, lower than
any previous Mars orbiter. To go directly into such an orbit instead of using
aerobraking, the mission would have needed to carry about 70 percent more fuel
when it launched.

The instruments on Mars Reconnaissance Orbiter will examine the planet from this
low-altitude orbit. A spectrometer will map water-related minerals in patches
as small as a baseball infield. A radar instrument will probe for underground
layers of rock and water. One telescopic camera will resolve features as small
as a card table. Another will put the highest-resolution images into broader
context. A color camera will monitor the entire planet daily for changes in
weather. A radiometer will check each layer of the atmosphere for variations
in temperature, water vapor and dust.

"The missions currently at Mars have each advanced what we know about the
presence and history of water on Mars, and one of the main goals for Mars
Reconnaissance Orbiter is to decipher when water was on the surface and where
it is now," said JPL's Dr. Richard Zurek, project scientist for the mission.
"Water is essential for life, so that will help focus future studies of whether
Mars has ever supported life."

The orbiter can radio data to Earth at up to 10 times the rate of any previous
Mars mission. Besides sending home the pictures and other information from its
own investigations, it will relay data from surface missions, including NASA's
Phoenix Mars Scout scheduled for launch in 2007 and Mars Science Laboratory in
development for 2009.

Additional information about Mars Reconnaissance Orbiter is available online at:

The mission is managed by JPL, a division of the California Institute of Technology,
Pasadena, for the NASA Science Mission Directorate, Washington. Lockheed Martin
Space Systems, Denver, is the prime contractor for the project and built the spacecraft.